1. Field of Invention
The present invention relates to a one-way wrench and, more particularly, to a one-way wrench switchable between two modes.
2. Related Prior Art
U.S. Pat. No. 6,070,499 discloses a one-way wrench switchable between two modes, one for transmitting high torque and the other for transmitting low torque. The one-way wrench includes a handle 11, a rotary member 27, a drive member 13, two pawls 42 and 43, a selector switch 45 and a drive ring 21. A knurled sleeve 12 is provided on a section of the handle 11. The handle 11 includes a fixed arm 14 formed on another section and a driving housing 15 formed at an end. The driving housing 15 includes teeth 17 formed on an internal face. The fixed arm 14 includes a tunnel in communication with the interior of the driving housing 15. The drive member 13 is a stepped element with two slots 39 and 40 for receiving the pawls 42 and 43. A pin 44 is inserted in the drive member 13 and the pawls 42 and 43 to render the pawls 42 and 43 rotatable relative to the drive member 13. The selector switch 45 includes a plate 52 formed at an end of a spindle 46. The spindle 46 includes two holes 55 and 56. The hole 55 receives a spring 49 and a bearing pin 47. The hole 56 receives a spring 50 and a bearing pin 48. As the selector switch 45 is inserted in the drive member 13, the holes 55 and 56 are in communication with the slots 39 and 40, respectively. The spring 49 pushes the bearing pin 47 to bias the pawl 42. The spring 50 pushes the bearing pin 48 to bias the pawl 43. A substantial portion of the drive member 13 is inserted in the driving housing 15 and the drive ring 21 while a portion of the drive member 13 that extends out of the drive ring 21 is engaged with a clip 36. Thus, the drive member 13 and the drive ring 21 are kept on the handle 11 while the drive ring 21 is allowed to spin around the drive member 13. The pawl 42 is engaged with the driving housing 15 while the pawl 43 is engaged with the drive ring 21.
The shaft 24 includes a bevel pinion 25 at an end and a spline projection 27 at another end. A substantial portion of the shaft 24 is inserted in the tunnel of the handle 11 while the bevel pinion 25 is engaged with the drive ring 21 in the driving housing 15 and the spline projection 27 is engaged with the knurled sleeve 12.
The knurled sleeve 12 is maneuvered to spin the shaft 24 relative to the handle 11 in two senses of direction. In the first sense of direction, the bevel pinion 25 spins the drive ring 21 relative to the pawl 43 without spinning the drive member 13 in a direction. The bevel pinion 25 spins the drive ring 21 that in turn spins the drive member 13 via the pawl 43. Thus, the one-way wrench transmits low torque at high speed.
When the handle 11 is pivoted to spin the driving housing 15 while the shaft 24 is not spun relative to the handle 11, the driving housing 15 spins the drive member 13 via the pawl 42. Thus, the one-way wrench transmits high torque at low speed.
Taiwanese Patent Nos. 494828 and 1468261 disclose similar one-way wrenches. However, problems are encountered in the use of these one-way wrenches. Firstly, in the mode for transmitting low torque at high speed, the actual speed for spinning the drive member 13 is low since a user cannot use his or her hand to spin the knurled sleeve 12 for more than 180° without having to stop and turn his or her hand back to the normal position. Secondly, the user could easily injure his or her wrist if he or she twists the knurled sleeve 12 very often.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.